1. Field of the Invention
The present invention relates to a transmission electron microscope.
2. Description of Related Art
Electron energy loss spectroscopy (EELS) is a technique consisting of irradiating a specimen with an electron beam and obtaining a spectrum from the intensities of loss energy of electrons transmitted through the specimen. The energy that an electron loses within a specimen varies according to the constituent elements of the specimen, how atoms are bonded to each other, and other factors. Accordingly, the structure of the specimen can be known from its spectrum. An energy filter can image electrons having certain energies from electrons separated according to energy and so this instrument has attracted attention (see, for example, JP A-2001-6601).
In a transmission electron microscope (TEM) equipped with an energy filter, devices such as a dark-field detector for scanning transmission electron microscopy (STEM) and optical parts such as an entrance aperture for limiting the field of view for electrons incident on the energy filter are preferably disposed at the entrance image plane of the energy filter.
However, because of mechanical restrictions, it is impossible to arrange an STEM dark-field detector, an entrance aperture, and other parts at the incident image plane of the energy filter. Therefore, such STEM dark-field detector and entrance aperture are located off the position of the entrance image plane of the energy filter.